After the end of the Boer War he returned to a regular posting with his regiment in August 1902,[4] and was appointed regimental Adjutant of the 1st Battalion on 3 September 1902.[5] He left South Africa with other men of his battalion on the SS Sardinia in September 1902.[6] Arriving at Malta the following month, he was engaged in Imperial garrison service there and at Crete before being accepted into the Staff College, Camberley in 1905. After graduation he served in a variety of positions as a staff officer, including as director of training at the War Office from 1908 to 1910, followed by two years as a staff major with the 5th Infantry Brigade. In 1912 he was transferred back to the Staff College, this time as an instructor.

On 6 April 1918, with the German Georgette Offensive imminent, he was sent on a mission to Beauvais to attempt to persuade Ferdinand Foch to take over the British line as far north as the Somme, to send French reserves behind British line at Vimy Ridge, or to conduct a major French offensive. Foch, concerned at the risk of a German attack in the French sector, refused, although he offered to participate in a joint Anglo-French offensive near Amiens.[8]

In the spring of 1918 Davidson, now a major-general, was promoted to control both Intelligence (formerly the empire of Haig’s alleged eminence griseJohn Charteris and now under Brigadier General Edgar Cox), and Operations (“Oa”, now under the future CIGS Brigadier General John Dill).[9]

Ahead of the Bluecher Offensive, Haig later claimed that he and Davidson had repeatedly warned of the dangers of a German attack along the Chemin des Dames, but that their warnings were brushed aside by Foch, Maxime Weygand and de Barescut. No evidence had been found to substantiate this claim.[10][11]

He left the army in 1922, and immediately stood for Parliament as a Conservative. He was returned for Fareham, and took an active role in the House of Commons army committee. He resigned in 1931 by appointment as Steward of the Chiltern Hundreds to concentrate on his business interests, including a seat on the Vickers-Armstrongs board and a position as chairman of the Bank of Australia between 1937 and 1945. In the early 1950s he published "Master of the Field", a defence of Douglas Haig's generalship in 1917 and 1918. He died in Daviot on 11 December 1954.[3]

^It should be noted that both British and French intelligence had believed that German March offensive against British Fifth Army, which was far larger and more effective than had been predicted, might be a feint before a bigger attack in Champagne, whilst Haig was quicker than Foch to realise that the German offensive on the Chemin des Dames at the end of May was serious. See Harris 2008 p443, 447.